SAS-6 is a cartwheel protein that establishes the 9-fold symmetry of the centriole
SAS-6 is a cartwheel protein that establishes the 9-fold symmetry of the centriole
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DOI：
10.1016/j.cub.2007.11.046
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发表时间：
2007-12-18
期刊：
影响因子：
9.2
通讯作者：
Hirono, Masafumi
中科院分区：
文献类型：
--
作者：
Nakazawa, Yuki;Hiraki, Madoka;Hirono, Masafumi
中心粒由九个三重态微管组成，它们以旋转对称的方式排列。这种结构在各种真核生物中高度保守，并作为纤毛轴突的基础。最近，一些蛋白质如SAS-6已被确定为中心粒组装早期过程中必不可少的[1,2]，但产生9重对称的机制尚不清楚。在秀丽隐杆线虫和果蝇中，SAS-6被认为在中心核前体的形成中起作用，中心管随后在其表面组装9个单线态微管。然而，中心管的普遍性尚不清楚，因为在许多其他生物中，中心粒组合中出现的第一个结构不是管，而是一个扁平的无定形环或一个轮毂和九个辐射辐条的侧轮结构。我们发现，在衣藻中，SAS-6蛋白定位于侧轮的中心部分，而SAS-6的零突变体bld12缺少这部分。有趣的是，这种突变体经常有中心粒；由7个、8个、10个或11个三胞胎加上9个三胞胎中心粒组成的我们推测，在许多生物体中，SAS-6是侧轮的重要组成部分，是一种稳定9-三重体结构的结构。
Centrioles consist of nine-triplet microtubules arranged in rotational symmetry. This structure is highly conserved among various eukaryotic organisms and serves as the base for the ciliary axoneme. Recently, several proteins such as SAS-6 have been identified as essential to the early process of centriole assembly [1, 2], but the mechanism that produces the 9-fold symmetry is poorly understood. In C. elegans and Drosophila, SAS-6 has been suggested to function in the formation of a centriolar precursor, a central tube that then assembles nine-singlet microtubules on its surface. However, the generality of the central tube is not clear because in many other organisms, the first structure appearing in the centriole assembly is not a tube but a flat amorphous ring or a cartwheel-structure with a hub and nine radiating spokes. Here we show that in Chlamydomonas the SAS-6 protein localizes to the central part of the cartwheel and that a null mutant of SAS-6, bld12, lacks that part. Intriguingly, this mutant frequently has centrioles; composed of 7,8, 10, or 11 triplets in addition to 9-triplet centrioles. We presume that, in many organisms, SAS-6 is an essential component of the cartwheel, a structure that stabilizes the 9-triplet structure.